Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015	Sep. 30, 2014
Numerator:
Income from continuing operations		$ 106,704		$ 13,168		$ 209,296	$ 39,896
(Income) Loss from continuing operations attributable to noncontrolling common units of the Operating Partnership		(1,945)		(193)		(3,850)	(635)
Preferred distributions		(3,313)		(3,313)		(9,938)	(9,938)
Allocation to participating securities	[1]	(367)		(432)		(1,200)	(1,285)
Numerator for basic and diluted income from continuing operations available to common unitholders		101,079		9,230		194,308	28,038
Income from discontinued operations	[2]	0		6,135		0	112,482
Income from discontinued operations attributable to noncontrolling common units of the Operating Partnership	[2]	0		(128)		0	(2,376)
Numerator for basic and diluted net income available to common unitholders		$ 101,079		$ 15,237		$ 194,308	$ 138,144
Denominator:
Weighted average common units outstanding - basic (Note 14)		92,150,341		83,161,323		89,077,012	82,525,033
Effect of dilutive securities		488,724		1,949,133		516,249	2,097,589
Weighted average common units outstanding - diluted (Note 14)		92,639,065		85,110,456		89,593,261	84,622,622
Basic earnings per unit:
Income (loss) from continuing operations available to common unitholders per unit - basic (Note 14)		$ 1.10		$ 0.11		$ 2.18	$ 0.34
Income from discontinued operations per common unit	[2]	0.00		0.07		0.00	1.33
Net income available to common unitholders per unit-basic (Note 14)		1.10		0.18		2.18	1.67
Diluted earnings per unit:
Income (loss) from continuing operations available to common unitholders per unit - diluted (Note 15)		1.09		0.11		2.17	0.33
Income from discontinued operations per common unit	[2]	0.00		0.07		0.00	1.30
Net income available to common unitholders per unit-diluted (Note 14)		$ 1.09		$ 0.18		$ 2.17	$ 1.63
Kilroy Realty, L.P. [Member]
Numerator:
Income from continuing operations		$ 106,704		$ 13,168		$ 209,296	$ 39,896
(Income) Loss from continuing operations attributable to noncontrolling common units of the Operating Partnership		(64)		(59)		(211)	(188)
Preferred distributions		(3,313)		(3,313)		(9,938)	(9,938)
Allocation to participating securities	[3]	(367)		(432)		(1,200)	(1,285)
Numerator for basic and diluted income from continuing operations available to common unitholders		102,960		9,364		197,947	28,485
Income from discontinued operations		0	[4]	6,135	[4]	0	112,482	[4]
Income from discontinued operations attributable to noncontrolling common units of the Operating Partnership	[4]	0		0		0	(13)
Numerator for basic and diluted net income available to common unitholders		$ 102,960		$ 15,499		$ 197,947	$ 140,954
Denominator:
Weighted average common units outstanding - basic (Note 14)		93,938,783		84,965,523		90,869,696	84,329,317
Effect of dilutive securities		488,724		1,949,133		516,249	2,097,589
Weighted average common units outstanding - diluted (Note 14)		94,427,507		86,914,656		91,385,945	86,426,906
Basic earnings per unit:
Income (loss) from continuing operations available to common unitholders per unit - basic (Note 14)		$ 1.10		$ 0.11		$ 2.18	$ 0.34
Income from discontinued operations per common unit	[4]	0.00		0.07		0.00	1.33
Net income available to common unitholders per unit-basic (Note 14)		1.10		0.18		2.18	1.67
Diluted earnings per unit:
Income (loss) from continuing operations available to common unitholders per unit - diluted (Note 15)		1.09		0.11		2.17	0.33
Income from discontinued operations per common unit	[4]	0.00		0.07		0.00	1.30
Net income available to common unitholders per unit-diluted (Note 14)		$ 1.09		$ 0.18		$ 2.17	$ 1.63

[1] Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

[2] The Company adopted ASU 2014-08 effective January 1, 2015 (see Note 1). As a result, properties classified as held for sale and/or disposed of subsequent to January 1, 2015 that do not represent a strategic shift are no longer presented as discontinued operations.

[3] Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

[4] The Company adopted ASU 2014-08 effective January 1, 2015 (see Note 1). As a result, properties classified as held for sale and/or disposed of subsequent to January 1, 2015 that do not represent a strategic shift are no longer presented as discontinued operations.